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Date: Sun, 18 Jun 2023 22:52:28 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: deller@....de
Cc: linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: [PATCH] video/hdmi: Reorder fields in 'struct hdmi_avi_infoframe'
Group some variables based on their sizes to reduce hole and avoid padding.
On x86_64, this shrinks the size of 'struct hdmi_avi_infoframe'
from 68 to 60 bytes.
It saves a few bytes of memory and is more cache-line friendly.
This also reduces the union hdmi_infoframe the same way.
Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
Using pahole
Before:
======
struct hdmi_avi_infoframe {
enum hdmi_infoframe_type type; /* 0 4 */
unsigned char version; /* 4 1 */
unsigned char length; /* 5 1 */
/* XXX 2 bytes hole, try to pack */
enum hdmi_colorspace colorspace; /* 8 4 */
enum hdmi_scan_mode scan_mode; /* 12 4 */
enum hdmi_colorimetry colorimetry; /* 16 4 */
enum hdmi_picture_aspect picture_aspect; /* 20 4 */
enum hdmi_active_aspect active_aspect; /* 24 4 */
bool itc; /* 28 1 */
/* XXX 3 bytes hole, try to pack */
enum hdmi_extended_colorimetry extended_colorimetry; /* 32 4 */
enum hdmi_quantization_range quantization_range; /* 36 4 */
enum hdmi_nups nups; /* 40 4 */
unsigned char video_code; /* 44 1 */
/* XXX 3 bytes hole, try to pack */
enum hdmi_ycc_quantization_range ycc_quantization_range; /* 48 4 */
enum hdmi_content_type content_type; /* 52 4 */
unsigned char pixel_repeat; /* 56 1 */
/* XXX 1 byte hole, try to pack */
short unsigned int top_bar; /* 58 2 */
short unsigned int bottom_bar; /* 60 2 */
short unsigned int left_bar; /* 62 2 */
/* --- cacheline 1 boundary (64 bytes) --- */
short unsigned int right_bar; /* 64 2 */
/* size: 68, cachelines: 2, members: 20 */
/* sum members: 57, holes: 4, sum holes: 9 */
/* padding: 2 */
/* last cacheline: 4 bytes */
};
After:
=====
struct hdmi_avi_infoframe {
enum hdmi_infoframe_type type; /* 0 4 */
unsigned char version; /* 4 1 */
unsigned char length; /* 5 1 */
bool itc; /* 6 1 */
unsigned char pixel_repeat; /* 7 1 */
enum hdmi_colorspace colorspace; /* 8 4 */
enum hdmi_scan_mode scan_mode; /* 12 4 */
enum hdmi_colorimetry colorimetry; /* 16 4 */
enum hdmi_picture_aspect picture_aspect; /* 20 4 */
enum hdmi_active_aspect active_aspect; /* 24 4 */
enum hdmi_extended_colorimetry extended_colorimetry; /* 28 4 */
enum hdmi_quantization_range quantization_range; /* 32 4 */
enum hdmi_nups nups; /* 36 4 */
unsigned char video_code; /* 40 1 */
/* XXX 3 bytes hole, try to pack */
enum hdmi_ycc_quantization_range ycc_quantization_range; /* 44 4 */
enum hdmi_content_type content_type; /* 48 4 */
short unsigned int top_bar; /* 52 2 */
short unsigned int bottom_bar; /* 54 2 */
short unsigned int left_bar; /* 56 2 */
short unsigned int right_bar; /* 58 2 */
/* size: 60, cachelines: 1, members: 20 */
/* sum members: 57, holes: 1, sum holes: 3 */
/* last cacheline: 60 bytes */
};
---
include/linux/hdmi.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/hdmi.h b/include/linux/hdmi.h
index 2f4dcc8d060e..3bb87bf6bc65 100644
--- a/include/linux/hdmi.h
+++ b/include/linux/hdmi.h
@@ -170,19 +170,19 @@ struct hdmi_avi_infoframe {
enum hdmi_infoframe_type type;
unsigned char version;
unsigned char length;
+ bool itc;
+ unsigned char pixel_repeat;
enum hdmi_colorspace colorspace;
enum hdmi_scan_mode scan_mode;
enum hdmi_colorimetry colorimetry;
enum hdmi_picture_aspect picture_aspect;
enum hdmi_active_aspect active_aspect;
- bool itc;
enum hdmi_extended_colorimetry extended_colorimetry;
enum hdmi_quantization_range quantization_range;
enum hdmi_nups nups;
unsigned char video_code;
enum hdmi_ycc_quantization_range ycc_quantization_range;
enum hdmi_content_type content_type;
- unsigned char pixel_repeat;
unsigned short top_bar;
unsigned short bottom_bar;
unsigned short left_bar;
--
2.34.1
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